The invention relates to a frequency converter for an energy flow from a three-phase network to a consumer for medium and high output voltages, with variable frequency, current and voltage outputs, fed from secondary windings of a transformer with one or more cells per output phase (R, S, T). For each output phase, each identical cell has a diode input rectifier circuit, an active harmonic filter, an intermediate-circuit capacitance, and a three-point DC/AC converter on the output side.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A Frequency converter for converting energy flow from a three-phase network to a three-phase consumer supply at variable frequency, current and voltage outputs, comprising: at least one cell per phase of said three-phase consumer supply; all of said cells being identical; each of said cells includes: a diode input rectifier circuit; an active harmonic filter; an intermediate-circuit capacitance; a three-point DC/AC converter on an output side; said DC/AC converter comprising NPC diodes; said active harmonic filter includes at least two input inductors, at least two series-connected controllable switches and at least two diodes for receiving sinusoidal line current input and for generating a controllable intermediate-circuit voltage for said intermediate-circuit capacitance; said intermediate-circuit capacitance has two series-connected capacitor groups; and a neutral lead of a star circuit formed from said secondary windings is connected to a central point of said series-connected controllable switches, a center point of said series-connected capacitor groups and said NPC diodes of said three-point DC/AC converter.
2. A frequency converter according to claim 1 , wherein said active harmonic filter includes two input inductors connected to a DC output side of said diode input rectifier circuit.
3. Frequency converter according to claim 1 , wherein said active harmonic filter includes three input inductors which are series-connected to said secondary windings of said transformer and an AC input side of said diode input rectifier circuit.
4. A Frequency converter for an energy flow from a three-phase network to a consumer with variable frequency, current and voltage outputs, comprising: an input transformer; means for feeding said energy to secondary windings of said transformer; at least three identical cells connected to said secondary winding of each phase of said three-phase network; said cell comprising: a diode input rectifier circuit; an active harmonic filter; an intermediate-circuit capacitance; a DC/AC converter on an output side; wherein an output of said DC/AC converter for said at least three identical cells for each phase are serially interconnected, and said serially connected DC/AC converter outputs for each phase are connected to a common star point: said active harmonic filter includes: an input inductor; at least one controllable switch; at least one diode for receiving a sinusoidal line current input and for generating a controllable intermediate-circuit voltage for said intermediate-circuit capacitance.
5. A frequency converter according to claim 4 , wherein said input inductor is connected to a DC output side of said diode input rectifier circuit and said active harmonic filter includes a diode and a controllable switch; and said diode is series-connected to said input inductor and said controllable switch is connected to a center point of said series-connected inductor and diode.
6. Frequency converter according to claim 4 , wherein said input inductor is connected to an AC input side of said diode input rectifier circuit, and said active harmonic filter includes two controllable switches connected back to back to two diodes.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
April 24, 2002
June 8, 2004
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